Restore all data analysis pages but display them in maintenance mode.
Users can see these pages in the navigation and access them, but they
show a maintenance message instead of trying to fetch data.
Changes:
- Create MaintenanceMode component for reusable maintenance UI
- Restore all deleted pages: explorer, metadatos, rawExplorer, panorama,
comparativa-cosechas, informe-ingresos
- Replace complex data-fetching logic with MaintenanceMode component
- Add "Mantenimiento" badges to navigation menu items
- Pages show clear maintenance message with technical details
- Users can still navigate to these pages without errors
This approach:
- Keeps the UI structure intact
- Shows users what features exist
- Provides clear communication about maintenance status
- Prevents confusion about missing features
- Easy to re-enable when data sources are reconnected
